2 Transactions. 



The following studies deal with cushion-plants in general. Lazniewski 

 (1896) published a short account of the leaf-anatomy of Haastia pulvinaris, 

 and Miss Low (1899) gave a detailed account of the structure of the same 

 cushion-plant. Laing and Blackwell (1906, pp. 424, 426, 428) have a brief 

 popular account of certain forms of Raoulia and Haastia, and call attention 

 to the growth-form being due to " environment and not to relationship " 

 (I.e., p. 430). Cockayne (1909, pp. 196-97) dealt with the cushion-form in 

 certain subantarctic plants, and the same author (1912, pp. 20-21) shows 

 the relation between the mat- and cushion-forms, and discusses the question 

 of epharmony and epharmonic convergence in the latter. More important 

 by far than any of the above is the work of Schroter and Hauri (1914), 

 which defines and classifies the various types of cushion-plants, gives a 

 systematic list of the cushion-plants of the world, and concludes with an 

 examination of the relation between habitat and the cushion-form with 

 regard to its being a xerophytic adaptation or the contrary. 



It may be noted that no part of the present paper is devoted to the 

 synecology of the area dealt with. This arises from the fact that the 

 author had no additional material for a closer description of the associations 

 than that given by Cockayne and himself in the paper cited above, to 

 which the reader who desires further information may refer. 



In concluding these brief general remarks I must thank most sincerely 

 Professor C. Chilton, C.M.Z.S., and Dr. L. Cockayne, F.R.S., from both of 

 whom I have received much valuable assistance and advice. • 



(B.) Terminology and Definition of Term " Cushion- plant." 



As the various growth-forms dealt with merge into one another, so that 

 exact classification is difficult, the term " cushion-plant " is here used as 

 a generalization to include cushion -plants proper, mat-plants, and similar 

 growth-forms. It is rather difficult at the outset to frame an exact defini- 

 tion of the term " cushion-plant " as applied to the types considered. The 

 exact significance of the term will appear after consideration of several 

 types. 



Warming (1909, p. 11) defines cushion-plants thus : '' Shoot-system 

 richly ramified, often with the branches densely packed to form hemi- 

 spherical cushions. Foliage leaves usually small, more or less evergreen, 

 remaining attached for a long time in a faded condition, and decaying 

 slowly. Buds open." 



Schroter and Hauri (1914, p. 618) give this definition : " Polsterpflanzen 

 sind perennierende, krautige oder verholzende, meist immergrune Chamae- 

 phyten von kugeligem, halbkugeligem oder flach-deckenformigem, kom- 

 paktem Wuchs. Die Zweige sind zahlreich, kurzgliedrig, bis weit herab 

 dicht und ununterbrochen von kleinen, mehr oder weniger unbeweglichen, 

 sitzenden, in mannigfaltiger Weise verwitternden Blattem bedeckt ; die 

 Zweige endigen in kontinuierlicher Flache und sind entweder dicht anein- 

 ander gepresst oder bei lockerer Stellung durch Fullmaterial verbunden. 

 So entsteht eine gewisse Festigkeit, Kompaktheit und Geschlossenheit des 

 sjanzen Individuums, das aus einer lebenden, dichten Decke liber einer 

 selbstgebildeten, verwitternden Fullmasse mit Schwammwirkung besteht." 



These definitions are certainly comprehensive, but for the present pur- 

 pose provisional definitions may be framed thus : A " mat-plant " is one 

 whose main branches lie prostrate on the ground and, as a rule, radiate in 

 all directions from a centre of growth ; the vertical branches are very 

 short and compacted together so that the plant forms a close mat of little 

 depth : while a " cushion -plant " has the same general form of growth as 



